Rapid radiographic roll film changer having a pressure platen actuated by air pressure

ABSTRACT

X-ray film is cyclically compressed, exposed, decompressed and advanced in a path between a platen and a film compression chamber and two intervening intensifying screens. A diaphragm on the chamber distends when subjected to air pressure and produces the contact pressure. A two-port rotary valve pressurizes the chamber, allows time for an exposure and exhausts the chamber for releasing the film. Another synchronously driven rotary valve has a port for projecting a pulse of air against the released film to form a loop in it and advance it from a preformed loop on the input side. A motor driven toothed-wheel forms the input loop from film in a feed magazine and advances the film output loop into a takeup magazine.

United States Patent Primary Examiner-James W. Lawrence AssistantExaminer-A. L. Birch [72] Inventor J0sephG.Quinn Milwaukee, Wis. Appl.No. 851,881

Attorneys-Ralph G. Hohenfeldt, Frank L. Neuhauser, Oscar [22] Filed Aug.21, 1969 B. Waddell and Joseph B. Forman [45] Patented Mar. 9, I971 [73]Assignee General Electric Company [54] RAPID RADIOGRAPHIC ROLL FILMCHANGER HAVING A PRESSURE PLATEN ACTUATED BY AIR PRESSURE ABSTRACT:X-ray film is cyclically compressed, exposed,

decompressed and advanced in a path between a platen and a gintensifying ds when subfilm compression chamber and two interveninscreens. A diaphragm on the chamber disten jected to air pressure andproduces the contact pressure. A two-port rotary valve pressurizes thechamber, allows time for an exposure and exhausts the chamber forreleasing the film. Another synchronously driven rotary valve has a portfor projecting a pulse of air against the released film to form a loopin,

nput side. A

p from film in tput loop into a H m @A WP N mG H MR F N "D.

it and advance it from a preformed loop on the i motor driventoothed-wheel forms the input loo a feed magazine and advances the filmon takeup magazine.

25,328 ll/l9l1 GreatBritain................ 1,285,860 12/1968Germany......................

PATENTEB MAR 9197:

3.569.700 SHEET 1 BF 5 Jmew/ar jo s dz )9. $10101 44 MM PATENTEU MAR9197:

SHEET u UF 5 JflVtn/ar 1052M g il/Ian Wanna PATENTEU "AR 9 I97! SHEET 5OF 5 RAND RABIOGRAPHIC ROLL FILM CHANGER HAVING A FRESSURE FLATENACTUATED BY A PRESSURE BACKGROUND OF THE INVENTION One method ofassessing the human cardiovascular system is to inject a radiopaque dyeand record its progress through the blood vessels or heart by taking oneor more rapid series of radiographs. In some cases, the radiologistdesires to expose as many as 12 film frames per second which means thatthe film must be advanced, compressed between two intensifying screens,exposed, released and advanced at a similar rate. Since the film isusually about 14 inches wide, it should be evident that a considerablemass has to be accelerated rapidly and stopped abruptly. Operation hasbeen extremely noisy with the mechanical film advancement mechanismswhich have been used. The noise is sufficient to justify forewaming thepatient and soundproofing the procedures room.

Prior film changers have other disadvantages besides being noisy.Sometimes they produce a nonuniform contact pressure between theintensifying screens and intervening film. This produces film blurring,especially near the edges. Events in the film advance cycle sometimesoccur at displaced intervals so that synchronization with a similar filmchanger, used in a biplane technique, is imperfect. This may result fromfree-play which is inherent in mechanical film advance mechanisms. Also,there is usually vibration which causes slight film blurring and loss ofresolution. Occasionally, there are variances in the time intervalbetween initiation of the first film frame in a sequence and injectionof the radiopaque dye in the vascular system.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a roll film changer that is capable of high frame rates and hasconsistent synchronization of the film compression, exposure, andadvancement steps regardless of frame rate.

Another object is to provide a film changer that is complete insofar asfunctional features are concerned but is, nevertheless, simple inconstruction and reliable.

A further object is to minimize the operational noise level of the filmchanger.

Additional objects are to provide a rapid film changer which is subjectto diversified and precise programming, which is easy to unload withfilm and otherwise requires little care, skill or attention on the partof the operator.

In general terms, the invention is characterized by a film changerhousing which is on casters for being positioned under an x-rayexamination table. The changer has a film feed magazine and a filmtakeup magazine. The film is automatically threaded over a film pathwaywhich has air operated film compression device in the exposure region. Arotary valve for pressurizing and exhausting the compression chamber ismechanically coupled with another rotary valve that projects a precisepulse of air against the film to advance it after exposure anddecompression are complete.

A single motor drives the rotary valves and some mechanically coupledtoothed film advancing wheels so that all moving parts maintain theirphase relationship regardless of filming rate.

Rotation of the toothed-wheels is initiated with the exposure sequenceand a free loop of film is thereby formed on the input side of thecompression chamber. The loop on the output side is also continuouslytaken up and fed into the takeup magazine by the toothed-wheels.

The pressurized air or other gas input to the rotary valves iscontrolled by electrically operated solenoid valves. Although the rotaryvalves are turning before anexposure sequence is initiated, they areinactive until the solenoid valves are opened. Once the solenoid valvesare opened, they remain open for the entire filming series of as many as12 frames per second.

Means are also provided for automatically threading the film from thefilm feed magazine and film takeup magazine.

A more detailed detailed description of a preferred embodiment of thenew roll film changer will now be set forth in reference to thedrawings.

DESCRIPTION OF THE DRAWINGS FIG. l is a perspective view of a typicalx-ray cardiovascular procedure arrangement showing two of the new filmchangers positioned for biplane examination;

FIG. 2 is a partial vertical cross section through one of the filmchangers;

FIGS. 3, 4, and 5 show the film and its advance mechanism schematicallyin various states during a threading and an exposure cycle;

FIG. 6 is an isolated perspective view of the rotatable valve shaft forthe valve which controls compression and exhausting of the filmcompression chamber;

FIG. 7 is a fragmentary perspective view of the stationary casting ofthe pressurizing and exhaust valve with the rotatable element of FIG. 6omitted;

FIG. .8 is a vertical section of the film compression chamber taken onthe line 8-8 in FIG. 2; and,

FIG. 9 is .a graph for demonstrating the operational sequence of therotating valves.

DESCRIPTION OF A PREFERRED EMBODIMENT In FIG. 1, the patient, not shown,is ordinarily supported on an x-ray transmissive table top 1. Thesupport for the table top has been omitted. One of the new film changersis under the table top for frontal examination. The changer comprises ahousing 2 and is supported on casters 3. When the changer is inposition, some pads 4 are brought down manually so that the changer issupported on the pads instead of the casters when in use. 7

In FIG. 1, frontal radiographs are taken when x-radiation projectsthrough a collimator 10 from an x-ray tube casing 11. Operation of thex-ray tube is synchronized with the film changer so that exposure willoccur only when the film is stationary and compressed between someintensifying screens in the changer.

Housing 2 has an opening 5 in its end for receiving a filmtakeupmagazine 6. This magazine is structurally the same as a film feedmagazine 26 which inserts into the other end of housing 2, as can beseen in FIG. 2. The film magazine has a slot 8 in its top through whichfilm may be fed in or out depending on whether the magazine is used tofeed or takeup film. Under slot 8 inside the magazine is a light seal,not shown, which permits carrying magazines between the changer and thedarkroom without permitting extraneous light to strike the film. Eachmagazine has a handle 7 for carrying it and for inserting andwithdrawing it with respect to housing 2.

Another x-ray tube casing l2 and a collimator 13 may be provided fortaking a rapid series of radiographs laterally of the body so thechangers may be operated in a biplane mode. Lateral radiographs arerecorded in a second film changer 14 which is carried by a stand 115.The stand also has wheels 16 and a set of foot pads 17 for placing itfirmly on the floor of the procedures room. Note that the changers arebeveled at their corners 18 so that their film planes will be nearlyintersecting and all parts of the patients anatomy above the plane oftable top I will be projected onto the film. The film in each changer isimmediately behind and in parallel with a face plate 19 which ispreferably a decorative x-ray transmissive laminated plastic material.The vertically positioned film changer 14 also has an opening 20 forinstalling and removing a film takeup magazine and another opening, notshown, as its bottom for inserting a loaded film feed magazine.

Refer now to FIG. 2 which shows a vertical section taken throughhorizontal film changer housing 2. Within the film changer housing is afilm feed magazine 26 which is shown without film in it. The magazine isremovably attached within the housing at 27 by any suitable means thatpermit a good light seal between a planar surface 28 and the exit slotfor the film. The magazine may be loaded in a darkroom with a coil offilm that is disposed inside a curved spring 29 which is expanded whenit is loaded and contracts to maintain the film fairly tightly coiled asit is fed out through slot 8. Each magazine contains a flat sided rubberroller 30 which is turned diametrically oppositely from the position inwhich it appears in this FIG. to effect a light seal against the filmand maintain the leader which projects from the magazine. The leader islong enough to project from the magazine. The leader is long enough toproject through a slot 31 and into the interspace 32 of a guide member33. A wheel 34 having several equiangularly spaced needle points 35projects through a suitable slot in film guide 33 to engage the film atits edge and advance the same when the wheel 34 is rotated under power.

leader of the film is in position for being engaged by needle points 35,film guide 33 is allowed to rock back under the influence of spring 36.Then the needle wheel 34 and another one 49 like it are power-driven sothat the film 67 is threaded from feed magazine 26 to takeup magazine 6as depicted in FIG. 3.

During normal operation, a loop is formed in the film immediately afterit leaves film guide 33. An input loop cavity 21 is provided for thispurpose. It has a loop-forming guide 22 near its bottom which shapes thefilm as can be seen best in FIG. 4. After the loop is formed in thefilm, it projects into a guide slot 23 near the top of the input loopcavity 21 where it is admitted to the interspace between a platen 62 anda film compression device which will be described in more detail later,and is generally designated by the reference numeral 39 in FIG. 2.

During automatic threading, the film must be transported in its mostdirect path from feed magazine 26 to the film takeup magazine 6. Toassure that the film will thread automatically through the changerwithout forming loops at first, suitable deflectors 40 on the feed sideof compression chamber 39, and 41 on the output side of chamber 39, areprovided. Since both deflectors 40, 41 are similar in construction andoperation, only the former will be described. Deflector 40 is a thinsheet of phosphor bronze or other spring material which has a cord 42attached to it. The cord is wound around a pulley 43 behind which, butnot visible in FIG. 2, is a small cylindrical motor which is energizedonly during the first stage of automatic film threading. When the motoris energized, cord 42 is wound on pulley 43 and the deflector 40 isbrought over to nearly contact a curved surface 44 to offer furtherguidance to the film as it is proceeding toward and into slot 23 on theinput side of the compression chamber 39. This may be visualized best inFIG. 3. A similar motor and pulley 45 winds up a cord 46 to bring overdeflector 41 in the output loop chamber 47. On the output side, there isanother film guide 48 to direct the film into takeup magazine 6 and afilm advancing wheel 49 with needle points 50 for propelling the film.

Automatic film threading is initiated by pressing a button on aprogrammer, not shown, after the film leader has been started into inputfilm guide 33. This causes the deflectors 40, 41 to take their guidepositions automatically and starts a main drive motor 56 which drivestoothed-wheels 34 and 49 through the agency of a clutched pulley 57 anda pair of belts 58 and 59. Present, but not shown, in the region ofoutput film guide 48, is a sensor that detects the presence of theincoming film and turns off motor 56 after a predetermined time lapsewhich permits film to enter takeup magazine 6 and begin winding a coilof about one turn within it. At this time, deflectors 40, 41 returnautomatically to the position in which they are shown in FIG. 2 and thefilm is clamped momentarily by compression chamber 39 so as to permitthe last revolutions of motor 56 to form a loop in input cavity 21. Thecondition of the film that prevails at this time may be seen in FIG. 4.The changer is now substantially ready for a rapid film series.

In FIG. 2, that portion of the film which is ready for an x-ray exposureis in the interspace 61 between the film compression chamber 39 and thepressure platen which is generally designated by the reference numeral62. A cross section of the pressure chamber 39 and platen 62 is shown inFIG. 8, which will now be discussed. The platen 62comprises an aluminumframe 63 on which a plate 64 of beryllium or aluminum or other x-raytransmissive material is brazed at 65. Adhered to the face of plate 64is a thin x-ray image intensifying screen 66. The screen, of course,produces a fluorescent replica of the x-ray image and aids in exposingthe film. The film 67 passes through the interspace 61 and is subject tobeing pressed from the center of the exposure area toward its edges by adistensible metal diaphragm 68 which is part of the film compressionchamber 39. Diaphragm 68 is preferably milled to a thin cross sectionfrom a thicker piece of sheet stock so that the end product will be thinover most of its area and perfectly planar. Adhered to the face ofdiaphragm 68 is another intensifying screen 69 which serves the samepurpose as its counterpart on the platen.

Diaphragm 68 is fastened to an annulus 70 by means of suitable clampingmembers 71. .Annulus 70 is also clamped and sealed to a lower ring 72 inwhich there is a long slot or port 73 for admitting air or other gasunder pressure beneath the diaphragm 68 to distend or bulge it. Ring 72rests on another flat base member 74. Member 74 has a port 76 whichaligns with port 73 so that pressurized air may be admitted andexhausted from the pressure chamber. Any pressurized fluid could beused, including bottled gas, but use of air is preferable forconvenience and economy. Member 74 has s circular central opening towhich is welded an axially extending hollow cylinder 77 in which thereis a central bore 78. The bore is covered on top with a planar piece oflaminated plastic 79 and there is a suitable gasket 80 around cylinder77 for preventing leakage. The assembly may be secured in a leakproofmanner on the film changer casting by tightening of circularly spacedmachine screws 81. Silicone adhesiveis used as a sealant in most jointsthat are intended to be leakpr'oof.

Annulus 70 is provided with a plurality of axially extending andcircumferentially spaced expansion slits 86. There is a coating 87 ofrubber sealant on the inside of annulus 70 which prohibits air fromleaking through slits 86. The annulus 70 may be made of fiber glass orother material that is capable of flexing. When the interior of thechamber is pressurized to distend diaphragm 68, contact is first madewith the film at the center of the diaphragm and the contact areaspreads out toward the edges in an instant. However, because thediaphragm 68 is metal, there is a practical limit to the amount which itmay be distended and it is, therefore, necessary to let the annulus 70expand axially which it can do by letting its curved cross sectionexpand radially. The slits 86 that are disposed around the annuluspermit this to happen with least resistance. Internal air pressure alsotends to expand the inwardly concave annulus outwardly. This extends itsaxial dimension and develops a uniform high contact pressure from thecenter to the edges of intensifying screens 66 and 69 during filmexposure.

The x-ray permeability of the platen 62 and the top of pressure chamber39 is such that use of an image intensifier, not shown, is permitted.The outside diameter of the intensifier may nearly equal the bore 78 inFIG. 8. As can be seen, the construction of the pressure chamber is suchthat intensifier may be brought up to the bottom of plastic plate 79which is close to the plane of the film. The intensifier is omitted fromFIG. 2, but it would extend through a hole 91 in partition plate 23 andup into the interior of the film compression chamber 39 as indicated inFIG. 8. It should be noted that the pressure chamber is especiallydesigned to have a small air volume which comprises the volume betweenthe outside of cylinder 77 and the inside of annulus 7i) and the smallvolume between plastic plate 79 and diaphragm 68. This not onlyconserves the use of pressurized gas or air but permits more rapidexpansion of the diaphragm and exhaustion of the pressure chamber. In acommercial embodiment, even at a frame rate of 12 per second, about 50percent of each complete film advance cycle is available for x-rayexposure owing to rapid film transport and rapid operation of the filmcompression chamber at a gauge pressure of about 6 pounds per squareinch.

Pressurizing and exhausting the film compression chamber 39 iscontrolled by a rotary valve shaft 92 which is shown isolated in FIG. 6and which is adapted to be installed in the casting 96 shown in FlGS. 2and 7. The valve shaft 92 is provided with a pair of angularly andaxially separated slots or ports 93 and 94. Slot 93 is for admitting airor other pressurized gas to the film compression chamber and slot 94 isfor exhausting it. The slots are isolated from each other by an O-ringseal 95 which resides in a suitable groove in the valve shaft. ln'FlGS.2 and 7 one may see that a casting 96 is provided with a groove orheader 97 which serves as a common passageway between I the valve shaftand the interior of chamber 39 for both exhausting and pressurizing.Header 97 has a slot 98 in its bottom which aligns with either the airinlet slot 93 or exhaust slot 94 of rotary valve shaft 92 depending onthe angle of shaft rotation.

in FIG. 7 one may see that pressurized air is admitted to the bottomperiphery of valve shaft 92 through a duct 99 which is surrounded bysome threaded holes 100 for connecting a flanged elbow 101 that can beseen best in FIG. 2. Pressurized air is turned on at the start of thefilm series and turned off at the end of a series by a solenoid valve102 which is shown only in FIG. 2. Thus, when solenoid valve 102 isopened, pressurized air will flow through duct 99, rotating port 93,stationary valve slot 98, header 97, and slot 76 to the interior ofcompression chamber 39. The width of these slots 98, as well as thewidths and locations of slots 93 and 94 are very carefully controlled.it is this dimensional control which allows the prescribed timing.l)uring the procedure, air pressure is continuously extant in slot 99.The alignment of slot 93 with slot 99 determines the times of admittanceand cutoff of air to the compression chamber. As valve rotationcontinues, the exhaust port 9% in rotatable valve shaft 92 alignswithslot 98, and permits exhaustion of the film compression chamber 39.The air is exhausted to the interior of the film changer housing from aduct 193 which can be seen best in HO. 7.

A basically similar rotating film advancement valve shaft 186 is alsoprovided as illustrated in FlG. 2. This valve has a single port 197 topass pressurized air from a header chamber 198 to a multisotted nozzle199 when the valve is in the proper angular position. Port 107 in filmadvance valve 196 is so phased with slots 93, 94 in rotary compressionvalve shaft 92 that a pulse of air can only be delivered for forming anoutput film loop in cavity 37 when compression chamber 39 issubstantially exhausted and the film is free to move. Note that thedevice could be made with only one rotary valve shaft in which case thecompression and exhaust ports 93 and 94 could be axially and angularlydisplaced on the shaft and the film advance port 197 could be furtheraxially displaced at a roper angle. This, too, assures synchronousoperation of the valves.

Both rotating valve shafts 92 and res have a pulley such as the onemarked lltl in FIG. 6. The pulleys are toothed to permit coupling bothrotary valves 92 and 106 for simultaneous and synchronous rotation witha timing chain or belt such as 1 11 in F IG. 2. This type of beltassures that the phase relationship between the rotatable valve shaftswill be maintained. The film advance rotary valve shaft 106 has anotherpulley which is driven with a belt 113 from a motor-driven pulley 32.Hence, in this particular construction, valves 92 and 1% rotate wheneverdriving motor 56 is energized. Fressurized air for advancing the film issupplied to header 293 through another solenoid valve 114. Unless valveil -l is open, no air pressure will be available to advance the film toform a loop in it even through film advance valve we is rotating.Solenoid valve 114 is opened at the start of a rapid film series andremains open until the end of the series. Air pressure for advancing thefilm is about 15 pounds per square inch in a commercial embodiment.

The toothed-film advance wheels 34 and 49 do not, however, rotate whenmotor 56 is energized unless an electrically operated magnetic particleclutch 115 is engaged. in a commercial embodiment, there are actuallytwo separately controlled clutches which operate simultaneously exceptduring the film loop forming stages. The clutch may be engaged andtoothed-wheels 34 and 49 rotated at the beginning of and throughout arapid film series so that a loop is always being formed in input cavity21. Film is continually being transported from the loop in output cavity47 to the takeup chamber 6 when radiographing is in progress.

Synchronized operation of the film changer is governed to a large extentby a voltage derived from a rotary shaft angular position sensor whichin this case is a potentiometer which is shown for convenience in FIG. 6as being mounted on valve shaft 92 that controls the film compressionchamber. With a suitable electronic processonnot shown, thepotentiometer output voltage signal is converted to one that varieslinearly with respect to rotational angleof the valve. Therefore, thevoltage amplitude an any instant corresponds with a definite angularposition for each rotating valve.

The voltage signal can also be compared with a similar one from anotherchanger for producing a control signal that enables taking precisealternate or simultaneous frontal and lateral x-ray exposures when thechangers are used in a biplane procedure. Each changer has a tachometer,not shown, which is used in conjunction with the control signal from thepotentiometer to maintain motor speed, synchronism between changers andthe desired frame rate in the sequence. These control functions arecarried on in a programmer which is not shown because it is not part ofthe present invention and can be devised by any skilled logic circuitdesigner.

The operating mode of the changer will now be considered in greaterdetail as an aid to understanding its construction. Assume that theradiologist has elected to take three rapid film series, each of whichis called a phase. For instance, he may set the programmer to take l2frames per second in the first phase and immediately follow with asecond phase at some other rate such as 10 frames per second, afterwhich the changer may pause for a set number of seconds and then proceedwith a third phase automatically at another rate such as 4 frames persecond-In a commercial embodiment, the operator may elect as many as 12frames per second in any phase and as few as one frame every 10 seconds.The whole range of filming rates is available in steps in each phase.

Before a phase begins, the x-ray tube and dye injector, not shown, aremade ready for operation. This means that the rotating anode of thex-ray tube is brought up to speed and its filament current is adjustedfor producing x-rays of the intensity desired during the ensuingexposures. An exposure is initiated by applying high voltage between theanode and cathode of the x-ray tube. The dye injector may be set toinject immediately before the first mm is taken or sometime thereafter.These are known elementary procedures which need not be describedfurther.

Assume that when the changer is made ready, the film 67 will be disposedas in FIG. 4. At this time there is an input loop in cavity 21 and nooutput loop in cavity 47. Motor 56 may now be running and turning bothof the rotating valves 92 and 106 which are not active unlesspressurized air is applied to them. The film remains quiescent.Toothed-wheels 34 and 49 do not tend to advance the film until clutch M5is energized.

Let us look at conditions that prevail right before the start of a phaseor, in other words, before the first radiograph in a contemplated rapidseries is taken. All events are reckoned from time 0 which is when therotating compression valve port 93 is a few degrees prior to beginningopening or aligning with stationary port slot 98. At time 0,potentiometer 120 produces a voltage output signal at which timeelectrical interlocks prevent taking an x-ray exposure because the filmis not compressed. The rotary compression valve must rotate until it isclosed after which the potentiometer output signal is proper to opencompression solenoid 102. In the next half revolution of rotating valve92, air will be supplied through its port 93 to the compression chamberand the film will be compressed. Pressure on the chamber is sensed witha pressure switch, not shown. The presence of pressure in the chamberthen allows the filmadvance solenoid valve 114 to open but he film isnot propelled by a pulse of air until the rotating film advance valve106 attains the proper angular position at which time the compressionchamber will be exhausted. The foregoing illustrates that a seriescannot be started unless there is adequate time reckoned from time 0 toallow for the operating time of the compression solenoid 102 to therebyassure that full pressure will be applied to the compression chamber.Starting every series at a definite point in time also assures that allevents will occur in their proper sequence.

In FIG. 9, the pressure on chamber 29 is plotted against the angularposition of the pressure port 93 in rotating valve 92. At zero angle,the compression valve begins to open and it becomes fully open at pointA. When the film is fully compressed at point A, the x-ray exposure isautomatically initiated and it may be sustained for an exposure intervalending at point C or at 108, at which angle the exhaust valve port 94opens. One may see in FIG. 9 that pressure on the film persists longenough to permit an x-ray exposure to continue for almost half the timethat it takes to cycle the changer. The proportion of exposure time tocycling time remains constant for all of the high frame rates becausemotor 56 runs at a constant speed that depends on the frame rate that isselected.

' At point C in FIG. 9, inlet valve port 93 is fully closed and theexhaust valve port 94 is about to open and relieve the pressure inchamber 39. This is depicted physically in FIG. 4 which shows the filmcompression chamber 39 still compressed and the exhaust port 94 ready toopen. In FIG. 4, one may see that the film advance valve port 107 is afew degrees in advance of opening when the exhaust valve port startsopening. An additional few degrees of rotation of both valves causes theexhaust valve to become fully opened as at point D on the graph in FIG.9 at which time the advance valve fully opens. This causes an outputfilm loop to be formed as shown in FIG. under the influence of the pulseof air that is projected through port 107 and multislotted nozzle 109.

Since the toothed-wheels 34 and 49 are running continuously during eachexposure sequence, a film input loop is constantly being formed and filmis also being constantly withdrawn from the output loop fed into takeupmagazine 6. Because the inlet and exhaust ports of the rotatingcompression chamber valve are angularly displaced from each other, thereis a dead period from the time that the exhaust valve closes, at point Bon the graph, to the beginning of the next cycle when the compressionvalve opens again at point F.

Since we have assumed in this example that the second phase would be ata slower frame rate than the first, motor 56 is automatically caused toslow down before the second phase begins. This speed change can be madein an instant because the DC motor 56 is supplied with full waverectified DC through controlled rectifiers which are subject to firingangle variation. This is conventional DG motor speed control apparatusand is, therefore, not shown.

Changing the speed of motor 56 results in the speed of thetoothed-wheels and rotating valves being changed so that the wholesystem remains in synchronism regardless of frame rate.

At the end of a phase, there may be a pause before the third phasebegins. The solenoid valves 102 and 114 are, therefore, closed at theend of the second phase and clutch 115 is disengaged so the film willnot be advanced by the toothed-wheels nor by film advance valve 106which continues to rotate.

When all phases are complete, both solenoid valves W2 and 114 close andpressure chamber 39 is exhausted. Motor 56 continues to run and clutchM5 remains engaged to drive the toothed-wheels until the output loopwhich includes the last frame that was exposed is driven into takeupchamber 6.

Means are provided for cutting the films so that the frames taken of agiven patient may beremoved for development in an individual film takeupmagazine. In FIG. 2, the cutoff means is seen to comprise a blade 122that is attached to a cable 123 connected with a pair of motor-drivenpulleys 124. When the pulleys rotate blade 122 translates across thefilm path and cuts the film.

At slow frame rates such as below l bframes per second, motor 56 isstarted and stopped for each frame exposure. The motor is energized andit cycles the changer to execute the film advance, compression, exposureand advance steps.

Sometimes the radiologist examines the patient with an xray imageintensifier before beginning a film sequence. The image may bevisualized on a television monitor, which is not shown, and isconventional. When theimage intensifier is used, of course, the filmframe which is in line with it and the compression chamber will beexposed. One may appreciate this by examining FIG. 8 which shows thatthe image intensifier would be behind the film. In the present design,whenever the intensifier is used, there is automatic film advancement toremove the single exposed film. This is achieved by energizing solenoidvalve 114 and quickly forming a new output loop to thereby expel theexposed frame before the first frame in the filming series can beexposed.

In summary, a rapid film changer has been described. It has a filmcompression chamber which may be expanded with any fluid, gas or air.Compression and exhaust of the chamber is controlled by a rotary valvewhich is positively coupled with another rotary valve that advances thefilm at the proper instant after exposure. All steps in takinga filmsequence are compelled to remain in the proper sequence. Timing signalsare derived from a potentiometer which is positively coupled to bothrotating valves to assure that phase relationships will be maintained.Operational sequence occur so rapidly that a large part of the time ofeach film cycle is available for making an x-ray exposure.

lclaim:

l. A rapid radiographic film changer for use in a diagnostic system thatinterposes an examination subject between an xray source and a film,said changer comprising:

a. film feed and film takeup means connected by a film pathway;

b. a film pressure platen that is adjacent and substantially parallelwith a portion of the film pathway and is adapted to transmit an x-rayimage to the exposure region of a film in the pathway;

c. a sealed film compression chamber having a diaphragm which isexpandable to press the exposure portion of a film against the platenwhen the interior of the chamber is subjected to gas pressure; i

d. a stationary film compression valve member having inlet and outletports, the inlet port communicating with a source of pressurized gas andthe outlet port communicating with the interior of the compressionchamber;

e. a first rotary valve member having a first through port forconducting pressurized gas from the inlet port to the outlet port andthe chamber when the ports of the stationary and rotary members begin toalign, said rotary valve member also having a through exhaust portangularly spaced from the first port for conducting gas from the outletport and the chamber when the exhaust port begins to align with saidoutlet port;

f. a stationary film advancing valve member having inlet and outletports, the inlet port communicating with a source of gas pressure andthe outlet port being adapted to discharge gas against film whichextends beyond said pressure chamber;

g. a second rotary valve member having a through port for conductingpressurized gas from the last named inlet port to the outlet port and tothe film surface whereby to periodically propel the film and form a loopin the film when the second rotary valve member hasa predeterminedangular relationship with respect to the first rotary valve member;

' means to rotate the same, whereby the rotary valve means affectsequentialexpansion of the compression chamber, exhaust of the chamberand agas blast against the film to advance the same.

h. motor means; and The invention set forth in claim 3 including:

i. means coupling said motor means and rotary valves for first andsecond electrically openable valves having presjoint synchronousrotation, whereby to pressurize and exsurized gas inputs and havingtheir outputs respectively haust said film compression chamber andsequentially connected to supply gas to the first port for compressionproject gas against the film to form said loop and advance the chamberand to the port fordischarging gas against the film. the film, the firstelectrically operable valve receiving a 2. The invention set forth inclaim 1 including: control signal to open it before the rotary valvemeans I a. a potentiometer having a revolving shaft coupled for reachesan angularposition where it can admit gas to the synchronous rotationwith said rotary valve members, chamber and the second electricallyoperable valve being said potentiometer being adapted to produce anoutput operated thereafter so that film will be advanced when electricsignal whose magnitude is indicative of the anguthe compression chamberhas been pressurized and exlar position of the rotary valve members;hausted. I

b. a first solenoid valve connected to the inlet of the com- .Theinvention set forth in claim 4 including:

pression valve and a second solenoid valve connected to a rotary Shaft mans angular position sensor adapted to the inlet of the film advancevalve, said first and second produce an output signal corresponding inmagnitude solenoid valves being opened in that sequence in response 0 wth t instantan ous angular position of the shaft to the potentiometersignal attainingpredetermined conmeans, operation of Said e ri y p leValves secutive magnitudes before the first film in a series of being inresponse to the signal level from said sensor. films is exposed, wherebyall functions in an operational 6. The invention set forth in claim 3wherein said film comcycle of the film changer are started andmaintained in a pression means comprises:

proper sequence and phase relationship.

3. A rapid radiographic film changer for use in a diagnostic system thatinterposes an examination subject between an xray source and a film,said changer comprising:

a. a film compression chamber and a spaced apart platen located next tothe pathway followed by the continuous 3 ame by means of the rotaryvalve means; Sheet of film as it is advanced step by step through the c.a thin metal diaphragm sealed over the other end of the changer;.annulus and adapted to dlstend into the film pathway b. rotary valveshaft means having first, second and third toward plate when the 'lPressumed;

diametrically through pom at different angles about the d. x-rayfluorescent screen means interposed between sald rotational axis, thefirst port being adapted-to admit pres- Platen and 831d iap ragm adacent the film pathway, surized gas to the chamber when at a certainangle of rotation, the second port being adapted to exhaust gas from thechamber as the shaft means rotates further and, the third port beingadapted to discharge pressurized gas against the film to form a loop inthe film when the shaft 40 means rotates still further, the said first,second and third ports operating in the stated sequence, respectively;and

c. motor means mechanicallycoupled with the rotary shaft 21. asemiflexible annulus having a radially inwardly curved cross section;

b. base means on which one end of the annulus is supported, said basemeans having a port for admitting pressurized screen means and the filmagainst the platen.

7. The invention set forth in claim 6 wherein said annulus has aplurality of circumferentially spaced axially extending slits wherebythe curved cross section of the annulus may expand radially and therebyincrease its axial dimension to enhance compression, and a pliablesealant covering said slits.

gas to the interior of the annulus and for exhausting the wherebydistension of the diaphragm will compress the v I

1. A rapid radiographic film changer for use in a diagnostic system that interposes an examination subject between an x-ray source and a film, said changer comprising: a. film feed and film takeup means connected by a film pathway; b. a film pressure platen that is adjacent and substantially parallel with a portion of the film pathway and is adapted to transmit an x-ray image to the exposure region of a film in the pathway; c. a sealed film compression chamber having a diaphragm which is expandable to press the exposure portion of a film against the platen when the interior of the chamber is subjected to gas pressure; d. a stationary film compression valve member having inlet and outlet ports, the inlet port communicating with a source of pressurized gas and the outlet port communicating with the interior of the compression chamber; e. a first rotary valve member having a first through port for conducting pressurized gas from the inlet port to the outlet port and the chamber when the ports of the stationary and rotary members begin to align, said rotary valve member also having a through exhaust port angularly spaced from the first port for conducting gas from the outlet port and the chamber when the exhaust port begins to align with said outlet port; f. a stationary film advancing valve member having inlet and outlet ports, the inlet port communicating with a source of gas pressure and the outlet port being adapted to discharge gas against film which extends beyond said pressure chamber; g. a second rotary valve member having a through port for conducting pressurized gas from the last named inlet port to the outlet port and to the film surface whereby to periodically propel the film and form a loop in the film when the second rotary valve member has a predetermined angular relationship with respect to the first rotary valve member; h. motor means; and i. means coupling said motor means and rotary valves for joint synchronous rotation, whereby to pressurize and exhaust said film compression chamber and sequentially project gas against the film to form said loop and advance the film.
 2. The invention set forth in claim 1 including: a. a potentiometer having a revolving shaft coupled for synchronous rotation with said rotary valve members, said potentiometer being adapted to produce an output electric signal whose magnitude is indicative of the angular position of the rotary valve members; b. a first solenoid valve connected to the inlet of the compression valve and a second solenoid valve connected to the inlet of the film advance valve, said first and second solenoid valves being opened in that sequence in response to the potentiometer signal attaining predetermined consecutive magnitudes before the first film in a series of films is exposeD, whereby all functions in an operational cycle of the film changer are started and maintained in a proper sequence and phase relationship.
 3. A rapid radiographic film changer for use in a diagnostic system that interposes an examination subject between an x-ray source and a film, said changer comprising: a. a film compression chamber and a spaced apart platen located next to the pathway followed by the continuous sheet of film as it is advanced step-by-step through the changer; b. rotary valve shaft means having first, second and third diametrically through ports at different angles about the rotational axis, the first port being adapted to admit pressurized gas to the chamber when at a certain angle of rotation, the second port being adapted to exhaust gas from the chamber as the shaft means rotates further and, the third port being adapted to discharge pressurized gas against the film to form a loop in the film when the shaft means rotates still further, the said first, second and third ports operating in the stated sequence, respectively; and c. motor means mechanically coupled with the rotary shaft means to rotate the same, whereby the rotary valve means affect sequential expansion of the compression chamber, exhaust of the chamber and a gas blast against the film to advance the same.
 4. The invention set forth in claim 3 including: a. first and second electrically openable valves having pressurized gas inputs and having their outputs respectively connected to supply gas to the first port for compression the chamber and to the port for discharging gas against the film, the first electrically operable valve receiving a control signal to open it before the rotary valve means reaches an angular position where it can admit gas to the chamber and the second electrically operable valve being operated thereafter so that film will be advanced when the compression chamber has been pressurized and exhausted.
 5. The invention set forth in claim 4 including: a. a rotary shaft means angular position sensor adapted to produce an output signal corresponding in magnitude with the instantaneous angular position of the shaft means, operation of said electrically operable valves being in response to the signal level from said sensor.
 6. The invention set forth in claim 3 wherein said film compression means comprises: a. a semiflexible annulus having a radially inwardly curved cross section; b. base means on which one end of the annulus is supported, said base means having a port for admitting pressurized gas to the interior of the annulus and for exhausting the same by means of the rotary valve means; c. a thin metal diaphragm sealed over the other end of the annulus and adapted to distend into the film pathway toward said platen when the annulus is pressurized; d. x-ray fluorescent screen means interposed between said platen and said diaphragm adjacent the film pathway, whereby distension of the diaphragm will compress the screen means and the film against the platen.
 7. The invention set forth in claim 6 wherein said annulus has a plurality of circumferentially spaced axially extending slits whereby the curved cross section of the annulus may expand radially and thereby increase its axial dimension to enhance compression, and a pliable sealant covering said slits. 